If you want to get full resolution the size is determined not by the camera.

For some people in some circumstances, size and weight of the camera kit is a factor that determines which kit to bring along.

In fact, based on Thom's writing, this is why he often takes his m4/3 equipment as opposed to his Nikon equipment. It's clearly not because he thinks he will get better IQ from his m4/3.

The point that several posters have made is that to just compare the A7r to the D800, without taking into account kit size and weight, when the justification for using m4/3 vs. D800 is size and weight, is not logically consistent.

The interesting thing to me is how many of the people who are in search of "ultimate image quality" and use m4/3 also own a D800 or Medium Format equipment.

It seems to me that in the best combination of almost ultimate IQ and relatively small size and weight. Thom either doesn't see it that way or did not make that point. This is what some of the posters are reacting to.